Fluid pressure spring device



July 9, 1940. s. L. c. COLEMAN FLUID PRESSURE SPRING DEVICE File d Oct.a, 1957 4 Sheets-Sheet 1 y 9, s. L. c. COLEMAN 2,207,088

FLUID PRESSURE SPRING DEVICE Filed Oct. 8, 1937 4 Sheets-Sheet 2 July 9,1940. s. L. c. COLEMAN FLUID PRESSURE SPRING DEVICE Filed Oct. 8, 1937 4Sheets-Sheet 5 July 9, 1940.

S. L. C. COLEMAN FLUID PRESSURE SPRING DEVICE Filed Oct. '8, 1957 PI E44 Sheets-Sheet 4 Patented July 9, 1940 UNITED STATES FLUID PRESSURESPRING DEVICE Stephen L. 0. Coleman, Fredericton, New Brunswick, CanadaApplication October 8,

11 Claims.

This invention relates to certain improvements in spring devices andparticularly to a combined fluid pressure and mechanical device of novelconstruction adaptable to all uses where it is desired to modify orcheck impact or rebound, the said device being capable of use alone as aunit, or in combination with any type of spring suspension in lieu ofthe conventional springs.

Broadly considered the object of this invention is to provide a lightdurable and efficient spring device combining in said structure, in anovel manner, the desirable properties or features of air and hydraulicpressure, together with certain mechanical instrumentalities forcontrolling and regulating said pressures.

Another object of the invention is to provide a combined pneumatic andhydraulic shock absorbing device which will eliminate the necessity ofusing, on various spring suspensions, comparatively heavy steelsuspension springs and separate shock absorbers.

A further object of the invention is the provision of a shock absorbingdevice of the fluid pressure type embodying built-in anti-frictionalbearings, so as to secure the softest possible action.

A still further object of the invention is to provide for automaticcontrol of the volume of confined oil under pressure, so that under agiven load the air pressure will remain practically constant.

It is' also another object of the invention to provide a self containedunit of such strength and dimensions that the average passengerautomobile can be sprung with the use of only two of such units,

The present invention is illustrated in the accompanying drawings inwhich:

Figure 1 is a vertical transverse sectional view of the improved device,

Figure 2 is a horizontal sectional view on line 2-2 of Figure 1,

Figure 3 is a horizontal sectional view on line 3-3 of Figure 1,

Figure 4 is a horizontal sectional view on line 44 of Figure 1,

Figure 5 is a view partly in section and partly in elevation of thefluid pump positioned on the right hand side of the main device as shownin Figures 1 and 2, and v 50, Figures 6 and 6A are vertical sectionalviews illustrating a modified form of air spring.

Referring to the drawings in detail the imor cylinder 2.

1937, Serial No. 168,088

Secured to the upper end of the tube l is a header block 3 provided witha semi-spherical seat 4 to receive a spherical member or ball 5 formedintegrally with a shank 6, said shank having a tapered portion 1 and areduced threaded end portion 8 to receive a nut or the like (not shown)by means of what the upper end of the device is secured to the mass tobe sprung. Through the longitudinal center of the ball 5 and the shank-6 there is a duct 9 provided with a grease gun fitting 10, whereby thenecessary lubricant is supplied through the duct 9 to the load bearingsurface of the ball and socket joint formed by the parts 4 and 5.

The header block 3 is primarily adjusted and secured in place within thetube I, by set screws II and i2, and then finally welded around its topcircumference as at l3 to make an air tight joint.

The ball 5 is held in position and adjusted to a proper workingengagement by the annular member l4 threaded into the header 3 as shown.The top surface of the adjusting annular member I4 is provided with aseries of spaced slots or grooves l5 and when said member I4 is properlyadjusted it is locked against rotation relative to the block 3, by akeeper plate or key 16 secured to said block 3 by a set screw or thelike H, the free end of said key being in engagement with one of theslots l5.

Secured to the lower end of the inner tube 2,

is ametal annular member or ring 18, tightly fitted around said tube andwelded thereto as at 19.

Tightly fitted within the lower end of the tube 2 is a relatively shortreinforcing tube section 20, the lower edge of said reenforcing tube andthe lower edges of the ring l8 being in the same plane with the loweredge of the tube 2. V

The upper edge of the reinforcing tube section 20 is constructed with aninwardly extending annular flange or head 2| provided with a series ofspaced ports 22, and the lower edge of said tube section 20 is formedwith an inwardly extending annular shoulder or flange 23.

Positioned within the tube 2 and concentric therewith is a smaller tube24 provided with a piston 25, said tube 24 having its lower end threadedinto the head 2| and locked therein by the cap-piece 26 also threaded.onto the lower end of said tube 24. The upper or inner end of the tube24 is provided with a welded in head or cap 21, through which operateswith a sliding fit, a rod 28 for the piston 25, the upper end of saidrod 28 terminating in an enlarged disk-like head 29 loosely fitting intoa slot 39 formed on a boss 3! carried by the header block 3.

Mounted adjacent the lower end of the tube 24 is a disk valve 32,adapted to cooperate with the annular shoulder or flange 23 forcontrolling the size of this central port. This disk valve 32 is firmlysecured to one end of a short rod or pin 33 passing with a sliding fitthrough a bearing in the center of the cap-piece 26, the opposite end ofsaid pin 33 having secured thereto a disk head 34 having a slidingengagement within the lower end of the tube 2A. A bleeder hole 35 isprovided in the cap-piece 26 or bottom of tube 24 for the purpose to behereinafter described.

The disk valve 32 is urged downwardly by a coil spring 36 and thisdownward movement and the size of the opening between the disk valve 32and the annular member 23 is regulated and governed by an adjustingscrew 31. This adjusting screw 3'! is provided with a lock nut 38 andpacking 39 and this outer end of the adjusting screw 3? is adapted to beenclosed and sealed within a cap nut 40.

These various parts just described in connection with the tube 26,comprise a dash pot tending to limit both extremes of the spring stroke.

Mounted between the telescoping tubes l and 2 is a ball bearing assemblycomprising an annular cage H providing a retainer for a large number ofballs =32, said assembly acting as an anti-frictional bearing betweenthese telescoping members. The balls are preferably placed at closeregular intervals in circles around the circumference of the retainingcage ii, the diameter of the holes in the cage being slightly largerthan the diameter of the balls so as to permit true rolling thereof.

Disposed around the lower outside portion of the tube 2, and concentrictherewith, is a coil spring 43 made of flat spring steel coiled on edge.The bottom or lower edge of this coil spring 33 is ofiset and turned upand said end is pivotally attached to tube 2 by a set screw or the likeM and the upper end of said spring is similarly constructed and attachedto the tube l by a set screw 45. The intermediate portion of the spring43 has secured thereto a pin or stub shaft 463, said pin d6 being alsosecured to the lower end of a rod or link M, the upper end of said link41 terminating in a ball 58 loosely fitting into a hole and slot in thebottom edge of the ball cage 5!.

Encircling the outer circumference of the tube adjacent the lower endthereof, and securely fastened thereto, is an annular flange or ring 49,said ring being shaped to form a seat-for an annular high pressureleather pump gasket 58 as shown. This gasket 50 is firmly securedagainst its seat 49, by a ring 5| which in turn is forced against thegasket 50 by a securing ring 52 threaded onto the lower outside end oftube l. The upper inner annular face of the securing ring 52 is providedwith a circumferential recess 53 in communication with bleeder ports 5 3also formed in the ring 52 and the lower end of the tube i. There isalso provided in the upper end of the tube 2, a bleeder port 55.

Securely threaded on the upper end of the tube 2 is a ring 56 providedwith an outside annular groove to receive a piston ring 51 which closesthe opening between the top of said tube 2 and the inner wall of thetube 5 and at the same time properly centers the tube 2 under workingcondition andprevents the air under pressure in chamber C from flowingdown between the walls of tubes l and 2, into chamber F which wouldnullify the restraining influence of disk valve 32.

concentrically disposed about the telescoping tubes l and 2 is anoutside tube or casing 58 said casing being spaced from the tube 1 andclosely embracing the packing ring 533 hereinbefore referred to. Thelower end of this casing 58 is provided with a solid bottom 59preferably welded thereto.

The annular member or ring it, secured to the bottom of the tube 2 hasfixed thereon a series of studs 60 projecting downwardly and passingthrough the bottom member 59 of the outside tube 58 providing the meansfor securing together the bottom 5!] and the ring it, and also acting asan attaching means, whereby the bottom of the complete device is securedor mounted in operative position by nuts or the like 6i, and positionedbetween the bottom member '58 and the ring i8, is a gasket 62 to preventleakage around the studs 60.

Mounted in one side of the device, between. the tube I and the outsidecasing or tube 58 is a fluid pump 63 the purpose of which is to behereinafter more fully explained.

With particular reference to Figures l5 and 6, this pump assembly 63comprises a plunger 64 the upper end of which being reduced and providedwith a guide bearing 65 and a stop washer 66 to limit its upward travel.This pistion 64 is normally held in its outward position by a flat,U-shaped spring 6'! and raises said piston after each downward stroke.The guide bearing is secured to the tube I by set screws as shown inFigure l, and a stop member 68 is secured inside 1:.

the top of the casing 58 by set screws or the like 69.

Cooperating with the piston fi l is a cylindrical bore H3 formed in thepump assembly and said assembly is also provided with a feed duct H fedby a port 12 said duct H at its upper end being in communication withthe cylinder ill through port 13. This pump assembly is also formed witha valve chamber 74 provided with a lift valve 15 normally held down by aspring it to seal the opening at the bottom of chamber 'Hl, and theupper end of the chamber 7 5 is closed by a plug or the like 11, whichat the same time forms a backing for the spring 16. Connecting thechamber 14 with the cylinder 10 is a horizontal duct or passage 18.

Disposed between the cylinder ID and the valve chamber M is an enlargedchamber '59, said chamber 19 being in communication with the valvechamber 14 through ports and 81.

Between the pump assembly and the adjacent face of the tube I there isprovided in the exterior wall of said tube l a duct or passage 82,connecting chamber 59 with the recess 53 provided in the securing ring52, which recess in turn being connected through ports 5:3 with theinterior of the outside tube or casing 58 as hereinbefore described.

This pump assembly 63 is brazed or otherwise securely fastened to theoutside face of tube 1 and bodily movable therewith during the operationof the device.

Extending upwardly from the upper end of the casing 58 is a flexiblebellows 83, the upper end of said bellows being attached to a hollowmetallic header or dome 84, surrounding and welded to the top of thetube l, whereby all dust and dirt will be excluded from the chamberwithin the casing 58. Just below the header 86, the

tube l is provided with an oil filler plug and 75 ber of ports til, 92,93, 94, 95 and 35m permitv the passage therethrough of eration of thedevice. r r

To prepare the air springfor use it is fully telescoped, and plug 85removed, and a charge of dewaxed oil is forced into the interior of thecase until it reaches the level of the filler port which is then closedby replacing plug 85. Air under pressure is then applied through airvalve"86 and the air spring is thereby extended raising oil during theopthe vehicle where the device isused in conn'ection with a vehiclespring suspension.' When fit reaches its normal height, which can beascertained by measurement, the cap of valve 85 is replaced, and thespring is ready for, use. Any air trapped at the top of chamber F belowgasket 59 is vented through the small bleeder ports 54 and escapesthrough vent 55 into main air chamber C. A quantity of oil is thenplaced in atmospheric pressure chamber H to bring it up to the level ofthe dotted line B, Bfand' to provide an oil seal and keep the leathergasket 58 in good condition.

In action when the sprung mass fall's, or the wheels rise to pass overan obstruction, the air spring is telescoped, and some of the oil in'chamber F is forced through ports 89 and 90 past disk valve 32 and pastports 22 into chamber E to rise above the dotted line A, A and itfurther compresses the air in air chamber '0 and D, when this action hasproceeded far enough to absorb the shock, the air gradually expandsagain to its original volume forcing the oil back past disk valve 32 andthrough the ports 89, and 98 into outside chamber F and the air spring Ireturns to its original normal length.

In case of a very violent shock the disk valve 32 can rise and compresscoil spring 36" thus giving a greater opening for the oil to passthrough and acting as a safety device to prevent excessive shock. Assoon as the oil stops flowing from outside chamber F into inside chamberE, coil spring 36 forces the disk valve down" against adjusting screw 31and the opening'past the disk valve 32 is restricted. This controls thespeed of the oil flow back from chamber E to F and consequently controlsthe speed of the rebound.

The amount of the set opening of disk valve 32 can be adjusted from theoutside, through the removal of cap nut 40, the looseningof lock nutwould require hardening and grinding to make a.

suitable surface for the ball bearings to operate upon. I

It is quite evident that the cage 4| acted upon by gravity, vibrationand constant changing ofthe direction of pressure, would in time fall tothe bottom of chamber F and be out of commission. To guard against thispossibility and 'yetnotinterfere with true rolling of the balls in thebearing, the simple half movement device is employed, consisting of thecoil spring 43 and drag link 41. If the top end of the coil spring movesa certain distance'it is quite evident that the center of the length ofthe spring'will move half as much in the same direction, therefore bytying one end of the coil spring to one telescoping tube, as at 45, andthe other end to the other telescoping tube, as at 44, and tying thecenter of the coilspring, as at at, by drag link M to retaining cage 4|,then the retaining cage will always be in its proper relative positionto the ends of its runway between tubes l and 2.

One advantage of an air-spring is its relative softness at the firstpart of its compression stroke and it is essential, in order to preservethis advantage, to eliminate as much static friction as possible, sothat the spring will start compressing without initial shock due tothisfriction. By employing a ball or roller bearing the greater part offriction is eliminated.

If the same volume of air is always retained in the air spring, thepressure will remain constant under the same load. 'In the air spring asillustrated in Figure 1, the air is not in contact with the leathergasket there being an oil seal extending far above the top of the.gasket. .Any

air which enters the oil through emulsification and rises to the leathergasket 58 will flow through ports 52 and rise between walls of tube land 2 until it reaches the abutment ring 56, it will then flow throughport 55 back into the main air chamber C. Through this means air will bekept away from the leather gasket 50.

In-course of time a certain amount of oil may, through seepage, workpast the leather gasket 55! into the atmospheric pressure chamber H andjoin with the oil that is already in there to the height of dotted lineB, B. When enough leakage past gasket takes place to raise the oil inchamber H so that it reaches the height of port 13 in the pump, Figure2, it flows through port 13 and charges the pump cylinder '10, then whenthe telescoping cylinders of the air spring lengthen through rebound orother cause, the

piston 64v and forces it down. This forces'the charge of oil out of pumpcylinder 18, through duct 18, raises valve 15, discharges through port8! into chamber 19, and from there it passes through duct 82 throughports 54 back where it came from in oil chamber F. The port 80 in thepump is for the purpose of letting the pressure in chamber 19, which isthe same as that in oil chamber F, in on top of valve 15 to supplementthe pressure of the coil spring I6 and keep valve '55 tight againstpossible leakage.

From the above it is apparent, that the volume of oil under pressureinside the air spring is maintained automatically. This being the case,the volume of air and its pressure, under normal load will not change,unless leakage develops in the air chambers which possibility is veryremote.

The double acting shock absorber is of very simple construction. Theresistance offered to the flow of oil past valve 32 on the compressionstroke of the air spring, is governed by the amount of opening betweenthe valve and its seat. The disk Valve 32 being held down in contactwith adjusting screw 3'! by the coil spring 35. the resistance offeredby'the-oil passing through the restricted opening about valve 32 can beconallowing screw 31 to be turned to raise or lower disk valve 32 asdesired.

On the expanding or rebound stroke of the air spring, the expanding airin chambers C and D forces oil out of chamber E down past valve 32,through ports 09 and 90 into chamber F thusrestoring the air spring tothe original length it had before the compression stroke. It is quiteevident that the amount of opening between disk valve 32 and its seat 23will restrict the speed of the flow of oil from chamber E to chamber F,and in so doing will govern the speed of rebound of the sprung mass.

The dash pct 24 with its piston 25 is to prevent metal to metal contacton either extreme of the air spring stroke. On the compression strokethe piston 25 approaches the bottom of the tube. On its way down itforces the oil out ahead of it through slots 02, 93, 92 and SI. As slotafter slot is passed the amount of opening for the escape of oil growsless so there is a progressive resistance. When finally the last slot ispassed by the piston 25, the only escape for the oil is past the piston,and this being a neat fit a lot of resistance is set up thus bringingthe parts to rest. When the piston passes port 9I there is a very heavypressure exerted on the disk 54 which holds disk valve 32 down firmlyagainst its adjusting screw and this increases the resistance againstbottoming by increasing the oil pressure in chamber F.

Referring to Figures 6 and 6A there is illustrated a modifiedconstruction of shock absorber or air spring. This air spring comprisesa metal tube i 3 having welded to it at its lower end, a circular flangeIOI, shaped to support the leather cup packing I02. A metal flange ringI03 is slipped over the end of tube I00 and is interposed between theleather cup packing I02 and a leather cup packing I05 and is shaped toprovide support for both of said cup packings, in conjunction with themetal ring I05, slipped over the bottom end of tube I05 and embracingthe leather cup packing I05. The lower end of the tube I80 is providedwith a metal cap I00 having an internal thread by means of which it isscrewed onto a corresponding thread on the outside of the bottom of tubeI00. When the cap I05 is screwed up tight, it firmly holds the pistonpacking assembly I52, I03, I00 and I05 in place, and prevents leakagealong the side of tube I35. At the bottom of cap piece I05 is an annularflange I25, which acts as a plunger for a dash pot I directly below itin the base of the air spring. Arranged in the bottom of the cap I08 aresmall ports I01 and I01. In ring I05 are provided small ports I08 andI08 communicating with a groove cut on the inside of said ring I05 andthus insuring registry with corresponding ports in tube I30.

The top of piston tube I50 is sealed by plug I30 welded thereto, and inthe center of said plug is a semi-spherical socket provided with a softmetal lining III! which seats ball joint III. An annular socket IIZembraces the top part of the ball III and is threaded into the top partof plug I00 which serves to retain the ball in place and furnishadjustment for the ball and socket joint. Socket I I2 is locked inadjusted position by means on top of plate I58 is another circularrubber pad H9 and on top of this is a steel circular plate I surmountedby a steel washer I2I, the whole assembly being firmly drawn together bya nut I22 threaded on the shank III. The hole in plate I58 is larger indiameter than the ring flange H5 of the plate IIB which passes throughit. This space is filled with rubber so there is no metal to metalcontact between the air spring and attached part. There is a duct I I I"drilled down through shank III and ball III and into the a top of ductIII" is screwed a grease-gun fitting Surrounding the tube I00 is acircular steel tube I24 forming the compression chamber in which thepiston on tube I00 moves up and down, and surrounding this tube I24 is acircular tube I25 providing the outside case for the complete assembly.The top of the tube I22 is spun over and fits around the piston tube I00with a very loose fit. The bottom of tube I24 is fixed to the outsidetube I25 by six blocks interposed between the two tubes and welded toboth of them, and two of these blocks I26 and I21 are shown in section.The top of the outside case I25 is swelled out to form an air reservoircurved-over edges thereof butting against tube I24 towhich it is welded.Just below this swelled out portion is a perforated annular plate I29welded fast to the outside tube I25 and the space between the six blockssimilar to I26 and I21 is closed by perforated plates (not shown) weldedto the blocks, and the space between these plates and annular plate I29is filled with brass or copper wool. I 30 is an air valve, and I3I anoil filler plug. On top of the tube I20 is a felt dust ring I32, forminga seal between tubes I00 and I26, held in place by a metal flange ringI33 secured by a number of screws or the like I30. I35 is an oil filler,and I36 is a fabric or rubber bellows to exclude dust and dirt. It issecured at its bottom by being placed beneath flanged ring I33 and atits top it is fastened to the plate I It by means of a metal ring I31fastened to plate I I6 by a number of screws I30.

A circular base plate I39 has formed integral with it, a raised annularflange hi0 near itsouter circumference over which the outside tube I25fits. Outside and below flange I55, there is a groove to accommodate asoft metal washer MI. Adjacent this point are six studs passing upthrough holes in the base plate I39 and screwed into the six blockswelded between tubes I24 and I25. One of these studs M2 is shownthreaded into plug I26, and another stud I23 is shown threaded into plugI21. The six studs mentioned combine to pull case I25 down firmly ongasket MI and seal the joint tightly. Each one of these six studs likeI42 has a gasket Hi2 between its head and the base plate I39 to preventleakage.

Raised above the body of the base plate I39 to a level with the bottomof tube I24 is an annular flange I44, and cooperating with the upperouter edge of this flange and thelower edge of the tube I24 is a flatannular valve member I45 adapted to close the annular space betweenthese parts.

I28, the upper This valve I45 is held up by four coil springs, two ofwhich are shown at I46 and I41, and is guided, and-its height governed,by four studs passing down through corresponding holes with a slidablefit, two of these studs being shownat I48 and I49. These studs arescrewed into threaded holes in the base plate I39 and their projectingends have a screw driver slot for adjustment, said adjustments beingmaintained by lock nuts as shown at I50 and I5I.

In the center of the air spring is a thick walled tube I52 ofcomparatively small diameter, the

bottom end of said tube being flanged and tightly seated in a cavity inthe center of ring I44, and secured by a stout threaded stud I53 passingup through a hole in the exact center of base plate I39, and screwedinto a thread on the inside of tube I52, the tube I52 passing, with aloose fit, up through a hole defined by the flange I06 depending fromthe cap I06. At the top end of tube I52 there is a stout ring I54threaded onto the outside of tube I52. Ring I54 has formed integraltherewith four projectingstub shafts I55, I56, I51 and I58 placed atequally spaced intervals around its outside circmnference, said stubshafts having mounted thereon a needle roller bearing, I59 and I60 beingthe cap pieces, [BI and I62 the needle rollers, and I63 and I64 theoutside cases of the needle roller bearings.

Between the annular flange I44 and I52, is a cavity I16 which acts as adash pot.

There are three ports I11, I18 and I19 through the wall of tube I52. Allthe space in tube I52 and tube I is full of oil, and all the space belowthe piston in tube I24 is full of oil, and there is an inch of oil ontop of the piston in tube I24. The level of the oil in-the outer chamberwhen the piston is in normal position is at the dotted lineW. X. and iskept there by air pressure in reservoir I28 and under full down strokeof the piston I50 the oil rises-to the dotted line U. V. Backing up theleather cup gasket I02, is a circular hard felt ring I80, and back ofthis is a waved circular steel spring I8I.

In the center of the air spring is a reciprocating pump composed of apiston rod I82 acting in the tube I83, mounted in a boss I84 on thebottom center of block I09, this joint being sealed against leakage.Piston rod I82 has a number of shallow sealing grooves I85 at its upperend to increase its efliciency. A threaded plug I86 is screwed into thebottom of tube I52, having a hole in its center of larger diameter thanpiston rod I82 which passes up through it, said rod having a flanged endI81 of greater diameter than the hole in plugv I86 and it is looselyheld between plug I86 and stud I53. This construction permitsself-aligning of the pump parts. 7

Associated with the upper end of tube I83 is a transverse conduit I88communicating with the interior of pump tube I83 leading at one end intothe Vertical bore I89 and at the other into the vertical bore I90. Athreaded plug I9I with a port through its center is screwed into thethreaded bore I80 until it seats below the level of conduit I88. Thebottom of plug I9I has a seat to accommodate a steel ball I92 whichactsas a valve for the port in the center of plug I9I. The ball I92 is heldup against its seat by a coil spring I93, and a port I94 connects" boreI89 with the interior of tube I00. The top of .bore I89 is sealed by athreaded plug I95. A conduit I96 is drilled down through one of the fourabutments inside tube I00, connecting bore I90 with-theatmos- .dition.

pheric'pressure-chamber between tube I00 and This same'conduit 188communicates with a conduit I96 provided with-a'steel ball I91 acting asa'valve to close this end of conduit I96. The

This box 202 is oil tight and oilcan enter it only through a port 203set at the height desired for the oil in the chamber above the pistonleather cup gaskets.

Needle valve 200is positioned and guided by i being passed, with a looseflt, through box 202 at its top and through partition 204 near itsbottom.

The vertical bores I89 and I90 pass down through the head block I09 andinto the vertical abutments I69 and I10 inside the tube I00.

. To prepare the air spring illlustrated in Figures 6 and 6A, for use itis fully telescoped, and plug I3I and plug I35 are removed, and a chargeof dewaxed oil is forced into the interior of the case until it reachesthe level of the filler port at I3I which is then closed. A little airpressure is put in the air reservoir I28'lthrough air valve I30, whichwill force the oil down in theoutside chamber and into the pistoncylinder (inside tube I24), passing also into tube I52 and tube I00through port I19. Any air trapped below the leather cup gasket I04 isvented through the small vents I08 and I08, and the chamber I00 is freedof air through the top vent at I94 by depressing ball I92 with a wirethrough bore I89. As soon as all the air is expelled from the insidetubeI00 the oil begins to flow, and the valve I92 is closed. A smallquantity of oil is' forced in through filler I35 on top oftheleatherpiston gasket I02, which acts as a seal and keeps'the leather in goodcon- The air spring is then placed in position and given its maximumstatic'load, after which air pressure is applied through valve I30 untilthe piston rises to its desired height. The air spring is then ready forservice.

' In action, when the bodyfalls or the wheels rise to pass over anobstruction, the air spring is chamber until the ,air pressure overcomesthe pressure of the oil. The shock which caused the telescoping of theair spring, having passed, the

air pressure forces the oil back into the piston cylinder and causes thepiston to rise to its original position. f H

In case of a very violent shock, thecircular valve I45 being supportedon top of coil springs I46 and I41, can recede and increase the valveopening in proportion to the force, thus. acting as a safety device. Assoon as the oil stops flowing from the piston cylinder I into theoutside air chamber, the coil springs forcefthe valve. I45 up to its setopening, Tli'eamount of opening of the valve I45 on the rebound strokeof the air spring is controlled by the magma and I49 and their mates,which studs'canbelengthened or shortened between the valve I45and thebase plate by loosening-locklnuts J50 and I5I, and

vtelescoped, increasing the pressure in the piston screwing them in orout. By this means the amount of opening of the valve I45 on the-rebound stroke can be set to suit, and controls the speed of flow ofthe oil and consequently the speed of the rebound stroke.

In any spring suspension in order to secure the utmost softness, it isnecessary to eliminate as much friction on the compression stroke aspossible, therefore great care has been taken in this air spring toeliminate friction. As stated in the specification where the piston tubeI38 passes through the top of piston cylinder I24 it has a very loosefit and there is no metal to metal contact. The telescoping contact istaken by the needle roller bearings mounted on rings I and I'M actingbetween telescoping tubes Illil and I52, resulting in a minimum offriction in these roller bearing contacts and there is no rubbingfriction except between the leather cup gaskets and the cylinder wall,and as these contacts are bathed in lubricant, friction is held to aminimum.

If an extremely heavy shock is received forcing a full compressionstroke of the piston, the plunger formed by ring I06 enters the dash potH6 in the base plate and prevents the possibility of a metal to metalcontact. Provision is made for a compression stroke of three inches fromthe normal static position and for an extension stroke of two inchesfrom normal static position.

It is desirable to keep the bearing points I54 and IM between thetelescoping tubes see and IE2 as far apart as possible so as to reducethe strain thereon under lateral thrusts. When tube I52 passes upwardfarther into the tube Hit, it will carry the spider ring lid with it,because there will be more friction between it and tube I52 than therewill be between the roller bearings on I'M and the channel tracks ontube Hill. on an extension stroke of the air spring from the normalstatic position, the center tube IE2 is drawn further out of piston tubeInd, being free to slide through ring I'M, this extension stroke beingcushioned and limited by the coil spring I15.

When the spider ring I74 is carried upward by a compression stroke ofthe air spring, provision has been made to prevent it coming intoviolent contact with the cap piece I66 on its return stroke. As soon asport I18 enters ring I86 it is closed, and as the spider ring I'Htclosely fits the channels in the tube IDE for a distance of two inchesfrom its bottom, a dash pot action is secured. The purpose of the smallports I01, It? is to prevent vacuum drag holding I'M against cap pieceI06 on the compression stroke of the air spring.

The rubber insulated joint at the top of the air spring will be veryeifective to eliminate high frequency vibration, because of the largearea of bearing surface. The unit pressure per square inch iscomparativelylow, and soft rubber can be used and the ball and socketjoint at the top of the air spring precludes the possibility of itsbeing subjected to any heavy destructive twisting stresses. Conditionsfor lubrication in the ball and'socket joint are perfect, because thereis no possibility of the lubricant escaping. There are no oil coatedsurfaces exposed to dust or dirt, the device being completely closed.The possibility of leakage of either oil or air is very remote, andbecause of the lack of serious friction in the device it should becapable of long and constant service.

In Figures 6 and 6A is illustrated a method of connecting the air springto a sprung mass through the medium of rubber insulation and it is to beunderstood that this same method is contemplated in connection with theconstruction as illustrated in Figure l.

I claim:

1. In a fluid pressure spring device, the combination with a casing, oftelescoping tubes within said casing, means for maintaining air withinthe upper part of said tubes, means for automatically maintaining aliquid at a predetermined level in the lower part of said tubes,antifrictional means positioned between the walls of said telescopingtubes, and. a positive seal between said tubes.

2. In a fluid pressure spring device, the combination with a casing, oftelescoping tubes within said casing, means for confining air within theupper part of said telescoping tubes and easing, means for automaticallymaintaining a'liquid at a predetermined level in the lower part of saidtubes and casing, antifrictional means positioned between the walls ofsaid telescoping tubes, and a positive seal between said tubes andbetween said tubes and easing.

3. In a fluid pressure spring device, the combination with a casing, oftelescoping tubes within said casing, means for spacing the walls of theouter telescoping tube from the walls of the easing, said meanscomprising a slidable fluid-tight seal, means for maintaining a liquidseal above said slidable fluid-tight seal, a slidable fluid-tight sealpositioned between the walls of said telescoping tubes and means forconfining a fluid within the telescoping tubes and casing underpressure.

4. In a fluid pressure spring device, the combination with a casing, oftelescoping tubes within said casing, a dash-pot comprising a cylinderconnected to one tube and a piston connected to the other tube andstepped openings in the walls of said cylinder, whereby a pressureresistance will be gradually built-up to automatically function as apositive stop only, upon the extreme inward and outward positions of thetelescoping tubes.

5. In a fiuid pressure spring device, the combination with a casing, oftelescoping tubes within said casing, means for maintaining air withinthe upper part of said tubes, means for maintaining a liquid at apredetermined level in the lower part of said tubes, antifrictionalmeans positioned between the walls of said telescoping tubes, means formaintaining said antifrictional means inoperative position and apositive seal between said tubes.

6. In a fluid pressure spring device, the combination with a casing, oftelescoping tubes within said casing, means for maintaining air withinthe upper part of said tubes, means for maintaining a liquid at apredetermined level inthe lower part of said tubes, an annularsubstantially floating ball bearing assembly positioned between thewalls of said telescoping tubes, means for maintaining said assembly ina predetermined position under all working conditions and a positiveseal between said tubes.

7. In a fluid pressure spring device, the combination with a casing,of'telescoping tubes within said casing, means for retaining a fluidwithin the telescoping tubes and casing, a pump body including acylinder carried by the outer telescoping tube within the casing andmovable therewith, a piston for said cylinder, a spring for normallymaintaining said piston in retracted position, a stop carried by saidcasing and movable therewith in position to engage and urgesaid pistoninwardly against said spring,

whereby during the operation of the complete device said pump will beautomatically operated by the relative movements in opposite directionsof said outer tube and casing.

8. In a fluid pressure spring device, the combination with a casing, oftelescoping tubes within said casing, means for retaining a fluid withinthe telescoping tubes, packing carried by the outer telescoping tubeproviding a slidable sealed joint between said tube and casing, meansfor maintaining a sealing fluid in the chamber above said packing, apump mounted in said chamber adapted to be operated by the telescopingaction of said spring device, said pump forming a communieation betweensaid chamber and the space below said packing, whereby upon the rise ofthe sealing fluid in said chamber above a predetermined level, said pumpwill automatically return said fluid to the space below said packing.

9. In a fluid pressure spring device, the combination with a casing, oftelescoping tubes within said casing, means for admitting a liquid intosaid tubes and casing, means for introducing air under pressure abovesaid liquid, a pump positioned between the outside tube and casing forautomatically maintaining said liquid at a predetermined level and anexpandible and contractable member connecting the upper end of saidcasing with the upper end of the outer telescoping tube.

10. In a fluid pressure spring device, the combination with a casing, oftelescoping tubes within said casing, means for admitting and retaininga liquid within said tubes and casing, means for introducing andretaining air under pressure above said liquid, 2. pump positionedbetween the outer tube and casing for automatically maintaining saidliquid at a predetermined level, an exp andible and contractable memberproviding a lower end of said casing and the lower end of the innertelescoping tube and a dash pot mounted within said telescoping tubes.

11. In a fluid pressure spring device, the combination with a casing, oftelescoping tubes within said casing, means for admitting and retaininga liquid within said tubes and casing, means for introducing andretaining air under pressure above said liquid, an expandible andcontractable member providing a closurebetween the upper end of saidcasing and the upper end of the outer telescoping tube, an annularpacking ring carried by the upper end of the inner telescoping tubeproviding a slidable seal between said upper end and the inner face ofthe outer telescoping tube, antifrictional means positioned between saidtubes, an annular packing ring carried by the lower end of the outertelescoping tube providing a slidable sealed joint between said tube andcasing, means for maintaining a sealing fluid inthe chamber above saidlast mentioned packing ring, a pump mounted in said chamber adapted tobe operated by the'telescoping action of said spring devices, said pumpforming a communication between said chamber and the space below saidpacking ring for maintaining said sealing fluid at a predeterminedlevel, a manuallyregulated and automatically operated valve between

